Add test fixture support

Adds the test fixture support and converts a few tests to exercise the
code and show how it works.

Bug: 181070625
Test: m nothing
Change-Id: I0a2b40fff93b6041f9aa8c4ef0aba91da1bc8bf3
diff --git a/android/android_test.go b/android/android_test.go
index 46b7054..68cb705 100644
--- a/android/android_test.go
+++ b/android/android_test.go
@@ -44,3 +44,5 @@
 
 	os.Exit(run())
 }
+
+var emptyTestFixtureFactory = NewFixtureFactory(&buildDir)